1. Field of the Invention
The invention relates to a reclosable packaging system for enveloping a product. More particularly, the invention pertains to a reclosable plastic film packaging system using a zipper and straight tear films that are capable of tear propagating along substantially straight lines in response to an applied force sufficient to propagate a tear in the films.
2. Description of the Related Art
Reclosable packages using zipper technology are well known in the art. A conventional reclosable package generally comprises a polymeric envelope comprising overlapping films which are sealed along its outer peripheral edges and having a flexible plastic zipper positioned inward from one of the edges. A plastic zipper generally comprises interlocking zipper tracks positioned below a top edge of the package for opening and closing access to an inner portion of the package. Some prior art packages have also been known to include a moveable slider adjoined to the zipper for assisting with engaging and disengaging the tracks of the zipper. For example, U.S. Pat. No. 5,896,627 discloses a high-strength plastic slider for a reclosable bag that is difficult to separate or pry loose from a zipper on which it has been mounted.
Reclosable bags using zipper technology are known to be useful for storing solid and/or liquid products. They are extremely useful for food storage in a refrigerator or freezer because zipper locking bags typically have very strong seals that are virtually impermeable to air, providing excellent oxygen and moisture barriers that prevent food from spoiling, while allowing easy access to the stored food product. Reclosable zipper bags have also been known to be used by food manufacturers in storing food products in stores for direct sale to consumers. For example, U.S. Pat. No. 6,206,571 teaches a flexible, reclosable bag for storing cereals. In applications such as these, it is generally necessary that the top edge of the package above the zipper be sealed to prevent tampering with the enclosed food product prior to sale. This feature is illustrated in U.S. Pat. No. 6,206,571 wherein a resealable pour spout is located below a sealed top.
When a sealed reclosable bag is used to store a product for sale to consumers, it is necessary that the bag be easily openable by the consumer once they purchase the product. A commonly employed technique for providing an easily openable bag having good tamper resistance includes perforating a portion of the bag between a top edge of the bag and the reclosable zipper and between the side edges of the bag, creating a removable strip above the perforated line. After purchasing the product at a store, the consumer may then tear the removable strip off of the bag revealing the reclosable zipper underneath, and allowing them to access the food product stored therein. Perforation of the film is desirable because it allows the consumer to tear the package along a straight line, allowing for complete removal of the removable strip so that the packaged food product can be easily poured out of the package if desired.
Various techniques have been known in the art to create such perforations, including microperforating and laser scoring. Microperforating involves the mechanical creation of tiny holes or perforations through a material to facilitate tearing along a straight line. Laser scoring involves the creation of tiny holes or perforations through the material using a laser rather than mechanically. Although these techniques are particularly useful for easily tearing the plastic in a particular direction, each has the disadvantage of compromising the integrity of the package by allowing microbes and other potentially dangerous organisms to penetrate the package. This is particularly undesirable when the packaged good is a food product for consumption by humans. Further, laser scoring techniques are also undesirable because they are very expensive to conduct. Therefore it would be desirable to provide a plastic bag that is capable of straight tearing without the need for microperforating or laser scoring a portion of the plastic.
The invention provides a reclosable film package comprising:
a) first and second overlapping straight-tear films capable of propagating a tear along a locus of points in one of two substantially straight perpendicular lines in response to an applied force sufficient to propagate a tear in the films, the films being sealed together at top, bottom, left and right edges defining an enclosure, the enclosure having sealed bottom, left and right margins extending for a distance away from the bottom, left and right edges toward a center of the films; each film comprising in order from an outside portion of the enclosure to an inside portion of the enclosure:
i. a nylon or polyester layer;
ii. optionally, an adhesive layer; and
iii. a sealant layer;
b) a reclosable zipper substantially parallel with and positioned below the top edge of the films and extending between left and right end points located at the left and right margins; said zipper comprising a first track on the first straight-tear film and a second track on the second straight-tear film, which first and second tracks are adapted to releasably engage each other;
c) a slider moveably attached to said tracks for engaging and disengaging the tracks between the end points;
d) left and right nodules positioned at the left and right end points; and
e) a tear propagation line extending from the left nodule to the right nodule substantially parallel along the zipper, and a tear propagation line extending from each of the left and right nodules substantially parallel along the left and right margins to the top edge of the films, defining a removable tear strip between the left and right margins and above the zipper.
This invention also provides a reclosable film package comprising:
a) first and second overlapping straight-tear films capable of propagating a tear along a locus of points in one of two substantially straight perpendicular lines in response to an applied force sufficient to propagate a tear in the films, the films being sealed together at top, bottom, left and right edges defining an enclosure, the enclosure having sealed bottom, left and right margins extending for a distance away from the bottom, left and right edges toward a center of the films; each film comprising in order from an outside portion of the enclosure to an inside portion of the enclosure:
i. a nylon layer;
ii. an adhesive layer; and
iii. a polyethylene layer;
b) a reclosable zipper substantially parallel with and positioned below the top edge of the films and extending between left and right end points located at the left and right margins; said zipper comprising a first track on the first straight-tear film and a second track on the second straight-tear film, which first and second tracks are adapted to releasably engage each other;
c) a slider moveably attached to said tracks for engaging and disengaging the tracks between the end points;
d) left and right nodules positioned at the left and right end points; and
e) a tear propagation line extending from the left nodule to the right nodule substantially parallel along the zipper, and a tear propagation line extending from each of the left and right nodules substantially parallel along the left and right margins to the top edge of the films, defining a removable tear strip between the left and right margins and above the zipper.
The invention further provides a process for forming a reclosable film package comprising:
a) forming first and second straight-tear films by attaching a nylon layer to a sealant layer optionally via an intermediate adhesive layer, said films having top, bottom, left and right edges;
b) forming first and second zipper tracks below and substantially parallel to the top edge of the films, said tracks having left and right end points and said tracks releasably engaging each other;
c) attaching a moveable slider to the tracks such that the slider is capable of engaging and disengaging the tracks between left and right end points;
d) adjoining the first and second straight-tear films by sealing the respective left, right and bottom edge of each film together such that the sealant layers are attached together, and forming left, right and bottom margins, thereby forming an enclosure; and
e) forming a left nodule at an intersection of a left zipper end point and the left margin, and forming a right nodule at an intersection of a right zipper end point with the right margin.
The present invention provides a solution to the problems of the prior art. The invention provides a package utilizing a straight tearing film that is easily tearable in a particular direction in response to a stress applied in that direction. The invention also allows for the direction of tearing to be easily changed in a direction perpendicular to the initial tearing direction to facilitate the fall removal of a tear strip above a reclosable zipper. The straight tearing films have good toughness, eliminates the need for perforating and provides an excellent barrier to oxygen and moisture while preventing contamination of the food product by microbes or other organisms.